A Greener View: Avoid putting paint on exposed wood

Q: My maple tree was pruned two months ago, while it was dormant during the winter. There is still sap running down the trunk where the branches were removed. The arborist said that we should not cover the wounds with paint, but I think the tree would be better off if the sap were to stop running. What do you think?

A: Your arborist is right. Don't put paint on the exposed wood. There are several issues here. First, many trees that are pruned will bleed for a while after limbs are removed. The sap helps wash away bacterial and fungal spores. The bleeding could go on for several months. Some species, like maples and birches, bleed longer than others. Some cut branches will bleed longer than others. The tree will not bleed to death. There is less bleeding now than there would have been if the pruning had been done during the growing season.

Second, cuts during the growing season attract insects that can bring bacteria and fungi to the tree, so a cut during dormant season is best.

Third, painting the tree will not stop the sap from bleeding. It would trap bacteria and fungi against the exposed wood, and it would trap moisture as well. This would allow the decay organisms to grow without your being able to see them. And the paint would damage some of the living tree cells, setting back the healing process. Without the paint, the exposed wood will dry off, and decay organisms will have a harder time surviving. New cells will heal over the wood and stop the bleeding.

Don't use tree paint on a fresh wound. Once the tree has developed a wall of healing tissue, fungicides and insecticides can be applied to the exposed wood. If desired, latex paint could be applied.

Q: I need to prune a few small ornamental trees. What is the best way to prune them?

A: It is best to start shaping trees while they are young. Here are seven pruning steps:

1. Remove the three Ds: damaged, dead and diseased branches.

2. Remove branches that are growing up next to the original trunk and trying to become new trunks.

3. Remove suckers growing up from the roots and water sprouts that are growing vertical off horizontal branches.

4. Remove branches that grow across the middle of the plant or interfere with other branches.

5. Remove branches that are growing parallel to another branch, especially if they are growing right over the top of another one.

6. Prune branches to direct them away from problems in the future, like those growing toward buildings or walkways.

7. Prune for shape if necessary.

Always prune back to another branch or a bud. There are buds at the point where leaves were attached to a branch. Even if there are no leaves, there should be small scars on the branch, evidence of where leaves were attached. These points are called nodes, and the branch between buds is the internode space. The internode space will usually just die back to the bud.